云南马厂箐铜钼矿成矿岩体的角闪石和黑云母矿物学特征及其意义  

Mineralogical characteristics of hornblendes and biotites in ore-forming porphyry from Machangqing Cu-Mo deposit in Yunnan Province and their significance

作　　者：沈阳[1] 郑远川[1] 马睿[1] 张爱萍 徐培言 吴昌炟 王梓轩[1] SHEN Yang;ZHENG YuanChuan;MA Rui;ZHANG AiPing;XU PeiYan;WU ChangDa;WANG ZiXuan(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;College of Resource Envi-ronment and Earth Sciences,Yunnan University,Kunming 650091,Yunnan,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]云南大学资源环境与地球科学学院,云南昆明650091

出　　处：《矿床地质》2018年第4期798-816,共19页Mineral Deposits

基　　金：国家重点研发计划项目(编号:2016YFC0600310);中国地质调查局地质调查项目(编号:DD20160024-07;DD20160026);青年科学基金项目(编号:41702091);国家重点基础研究发展计划"973"项目(编号:2015CB452600);国家自然科学基金项目(编号:41472076);基本科研业务费专项项目(编号:53200859424)的联合资助

摘　　要：马厂箐铜钼矿床位于扬子克拉通西缘,是三江成矿带内典型的大陆碰撞型斑岩铜-钼矿床,其成矿作用与矿区内的斑状花岗岩密切相关。在详细的岩相学观察基础上,对成矿岩体的造岩矿物角闪石和黑云母开展了电子探针成分分析,厘定了斑状花岗岩结晶的温压条件、岩浆氧逸度和含水量等要素,为解析马厂箐富碱侵入岩体的演化和成矿作用提供了矿物学尺度的制约。实验数据显示,岩体内角闪石富镁(w(Mg O)14.1%~16.3%)、富钙(w(Ca O)11.0%~11.6%)、贫钾(w(K2O)0.3%~0.6%)、富钠(Na2O/K2O>1.0),属于阳起石和镁角闪石。黑云母Fe2+/(Fe2++Mg)比值较为均一,集中分布在0.35~0.38之间,且显示出富镁(w(Mg O)13.6%~16.2%)、铝(w(Al2O3)12.9%~13.7%),贫钛(w(Ti O2)1.9%~3.0%)、钙(w(Ca O)<0.06%)的特征,属镁质黑云母。由角闪石和黑云母阳离子数计算的矿物结晶温度分别为687~770℃和660~713℃,结晶压力为38~82 MPa和55~80 MPa,相应侵位深度为1.3~2.7km和1.8~2.6 km。同时,通过角闪石成分计算岩浆氧逸度为ΔNNO+1.56^+2.41,并且根据岩石地球化学特征及矿物相稳定组合限定岩浆源区具有较高的含水量(w(H2O)>10%)。结合矿物组合中角闪石的大量存在,分析可知马厂箐斑状花岗岩具有高氧逸度、富水、侵位浅的特点,符合形成大型-超大型斑岩Cu-Mo矿床岩浆岩的基本特征。因此,继北衙超大型斑岩Au矿取得重大突破后,推测三江成矿带南段扬子克拉通一侧斑岩型Cu-Mo矿床仍有较大的找矿潜力。Located on the western margin of the Yangtze Craton, the Machangqing Cu-Mo deposit is a typical continental collisional porphyry Cu-Mo deposit in the Sanjiang metallogenic belt. The mineralization of Cu-Mo is closely related to porphyritic granite in the ore district. Based on the detailed petrographic observation, the authors investigated the composition of hornblendes and biotites from porphyritic granite by electron microprobe analysis （EPMA）. The critical factors for Cu-Mo mineralization such as temperature and pressure condition, oxygen fugacity and water content of magma were estimated, which provide the mineralogical constraints on the evolution and mineralization of alkali-intrusive rocks in the Machangqing deposit. The results show that hornblendes from porphyritic granite, which are rich in magnesium （MgO 14.1%～16.3%）, calcium （CaO 11.0%～11.6%） and sodium （Na2O/K2O〉1.0）, but poor in potassium （K2O 0.3%～0.6%）, belong to actinolite and magnesiohornblende. The characteristics of biotites are rich in magnesium （MgO 13.6%～16.2%） and aluminum （Al2O3 12.9%～13.7%）, poor in TiO2 （1.9%～3.0%） and calcium （CaO〈0.06%）, and the ratio of Fe2＋/（Fe2＋＋Mg） is homogeneous and between 0.35 and 0.38, suggesting magnesia biotite. The crystallization temperatures of horblendes and biotites from porphyritic granite are 687～770℃ and 660～713℃, crystallization pressures are 32～88 MPa and 55～80 MPa, and emplacement depth are 1.3～2.7 km and 1.8～2.6 km, respectively. The oxygen fugacity of porphyritic granite melts defined by hornblende components varies between △NNO＋1.56 and △NNO ＋2.41, and the results show that the water content of porphyritic granite melts are more than 10%. Combined with the presence of lots of hornblendes, the authors hold that the Machangqing porphyritic granite melts are characterized by high oxygen fugacity, waterrich and shallow emplacement, which is consistent with the basic features of large-gaint porphyry Cu-Mo deposits.

关 键 词：地球化学 斑状花岗岩 矿物学特征 氧逸度 含水量 马厂箐矿床 

分 类 号：P578.955[天文地球—矿物学] P578.959[天文地球—地质学]